The table is about 1.2M rows (its actively going up, so total rows grows slightly between iterations of this test, but that doesn't change the outcome).
mysql_num_rows is displayed - which is accurate, tested with select count(*) - after the pull query in order to show how large the result set is.
Then, a loop assigns the row to an array with mysql_fetch_array(). Iteration counter is incremented for every round, and you would expect it go get to mysql_num_rows and then break out of the while loop. Pretty standard stuff, been done a million times over.
What actually happens, on the other hand, is quite odd. It gets to exactly 1/2 way (floor(number_of_rows/2)) and then mysql_fetch_array() returns false. No matter how you limit the result set...
$iteration = 0;
$result = mysql_query("select `file_id`, `size` from `files`", $dbconn); // get all records
echo "\nDone. Found " . mysql_num_rows($result) . " rows."; // Done. Found 1291595 rows.
if ($result){
while ($line = mysql_fetch_array($result) !== false){
$iteration++;
}
echo "\ngot to $iteration before mysql_fetch_array was false."; // got to 642679 before mysql_fetch_array was false.
}
Sometimes $line is an empty array, sometimes mysql_fetch_array triggers false.
It gets mysql_num_rows that i'd expect and continues for 1/2 the records of the total result set size, then it stops...
If I put now, limit = 967356,1000000, I get:
Done. Found 324963 rows.
got to 162482 before mysql_fetch_array was false.
This is 1 off from being exactly 1/2 way.
limit = 1000000, 1000000:
Done. Found 292606 rows.
got to 146303 before mysql_fetch_array was false.
What in the world could this be?
php info:
php -v PHP 5.4.19-1+debphp.org~precise+3 (cli) (built: Aug 27 2013 14:29:42) Copyright (c) 1997-2013 The PHP Group
In order to avoid early termination of the while loop in situations where php will interpret the value of $line as false, change the line
while ($line = mysql_fetch_array($result)){
to
while (($line = mysql_fetch_array($result)) !== FALSE){
Another possibility is that you're running out of memory on very large result sets. Try using mysql_unbuffered_query instead of mysql_query().
Yet another possibility is that you have multiple database connections open in this script and mysql_query() isn't using the one you think it's using. Pass the optional 2nd argument to be sure. Change
mysql_fetch_array($result)
to
mysql_fetch_array($result, $dbconn)
Collected from the Internet
Please contact [email protected] to delete if infringement.
Comments